Power supply and pickup system capable of maintaining stability of transmission efficiency despite changes in resonant frequency

ABSTRACT

The present invention relates to a power supply and pickup system capable of maintaining stability of transmission efficiency despite changes in a resonant frequency. More particularly, the present invention relates to a power supply and pickup system capable of maintaining the stability of efficiency of transmitting power to a pickup device from a power supply device even when a voltage or current changes by the variation in a resonant frequency. According to the power supply and pickup system of the present invention, Q-factor of a power supply and pickup system is set to a low value, a stability of efficiency of transmitting power to a pickup device from a power supply device is maintained even when a voltage of current changes by the variation in a resonant frequency.

TECHNICAL FIELD

The present invention relates to a power supply and pickup systemcapable of maintaining stability of transmission efficiency despitechanges in a resonant frequency. More particularly, the presentinvention relates to a power supply and pickup system capable ofmaintaining the stability of efficiency of transmitting power to apickup device from a power supply device even when a voltage or currentchanges due to the variation in a resonant frequency.

DESCRIPTION OF RELATED ART

For the existing wireless power transmission devices, such devices thatobtain the maximum efficiency of transmitting power by correctly fixingpower supply devices and pickup devices and increasing the value ofQ-factor for optimum power transmission between power supply devices andpickup devices have been suggested. But the resonant frequency of systemis often changed depending upon the manufacturing process or errors inthe components used. Especially, for wireless power transfer electricvehicles traveling on the road with a feeder cable laid under the roadwhile being supplied with power from the feeder cable, power supplydevices are fixed but pickup devices are very hard to be correctly fixedand sometimes two or more pickup devices are installed in vehicles topickup more power. In such cases, resonant frequency of system may bechanged and the efficiency of transmitting power to a pickup device froma power supply device drops considerably.

DESCRIPTION OF THE INVENTION Technical Task

In order to solve the abovementioned problem, the purpose of the presentinvention is to set Q-factor of a power supply and pickup system to alow value and provide the power supply and pickup system capable ofmaintaining stability of transmitting power from a power supply deviceto a pickup device even when a voltage or current changes due to thevariation in a resonant frequency.

Means to Solve the Task

In order to achieve the abovementioned purpose, the first embodiment ofthe present invention provides a power supply device which suppliespower using electromagnetic induction to a moving object according tothe present invention including a power supply core with magnetic polesto form magnetic field in a particular direction; and a power supplycoil on which current flows with neighboring magnetic poles of differentpolarity, and is determined by said

$Q_{S} = \frac{{wL}_{S}}{R_{S}}$

and said w is the angular frequency of said power supply coil current,said L_(S) is the inductance of said power supply coil, and said R_(S)is the resistance of said power supply coil.

The second embodiment of the present invention provides a power supplydevice which supplies power using electromagnetic induction to a movingobject including a power supply core which has multiple magnetic polesin parallel to a traveling direction of the moving object and arrangedside by side with each other, and a power supply coil which is arrangedby extension in the traveling direction of the moving body and haselectricity flow so that the neighboring magnetic poles of said powersupply core on the surface perpendicular to the traveling direction ofthe moving object have different polarity, and Q-factor by said powersupply coil current is less than 100 and the Q-factor is determined by

${Q_{S} = \frac{{wL}_{S}}{R_{S}}},$

and said w is the angular frequency of said power supply coil current,said L_(S) is the inductance of said power supply coil, and said R_(S)is the resistance of said power supply coil.

The section perpendicular to the traveling direction of a moving objectof said magnetic pole may have a U-shaped form and said power supplycoil may be arranged in parallel to the traveling direction of a movingobject in said U-shaped magnetic pole.

The section perpendicular to the traveling direction of a moving objectof said magnetic pole may have two U-shaped forms adjoining each otherand said power supply coil may be arranged in parallel to the travelingdirection of a moving object in each of said U-shaped magnetic poles.

Said power supply core may have a form in which power supply moduleshaving multiple magnetic poles in parallel to the traveling direction ofa moving object and arranged side by side with each other are arrangedin series in the traveling direction of a moving object.

The third embodiment of the present invention provides a power supplydevice which supplies power using electromagnetic induction to a movingobject including a power supply core which has more than one magneticpole arranged in series in the traveling direction of a moving body, anda power supply coil which is arranged in parallel to the travelingdirection of a moving body on the left and right side of said magneticpoles and intersected with each other between said magnetic poles andhas electricity flow so that the neighboring magnetic poles of saidpower supply core in the traveling direction of a moving object havedifferent polarity, and said Q-factor is determined by

$Q_{S} = \frac{{wL}_{S}}{R_{S}}$

and said w is the angular frequency of said power supply coil current,said L_(S) is the inductance of said power supply coil, and said R_(S)is the resistance of said power supply coil.

The section perpendicular to the traveling direction of a moving objectof said magnetic pole has a T-shaped form, it is desirable that saidpower supply coil is arranged in parallel to the traveling direction ofa moving object on the left and right side of each of said magneticpoles and intersected with each other between said magnetic poles andelectricity of opposite directions flows on said power supply coils onthe left and right side of each of said magnetic poles.

Said power supply device may have an additional linear magnetic shieldmember installed in the traveling direction.

Said power supply core may be of such a form that power supply moduleswhich have one or more magnetic poles arranged in series in thetraveling direction of a moving object are arranged to make lines inseries in the traveling direction of a road.

Said power supply modules may have core connection part in the front andrear ends and each of the power supply core modules may be connected toeach other by said core connection part and arranged to make lines inseries in the traveling direction of a road.

Said power supply core may be arranged spaced apart from each other toaccept thermal expansion and thermal contraction.

Said power supply core may have fiber reinforced plastic installed inthe upper or lower part.

Said power supply core may have the width perpendicular to the travelingdirection of a moving object less than one half of the interval betweenthe centers of said magnetic poles.

It is desirable that the length of said magnetic pole in the travelingdirection of a moving object is more than twice of the distance betweenthe adjoining ends of said neighboring magnetic poles.

The fourth embodiment of the present invention provides a pickup devicewhich receives power using electromagnetic induction from a power supplydevice installed in the traveling direction of a moving object and isinstalled in a moving object, consisting of a pickup core which isinstalled spacing apart from a power supply device in the lower part ofa moving object, and a power supply coil which is installed in a loopform in said pickup core to allow current induced from a power supplydevice to flow, and Q-factor by said pickup coil current is less than100 and said Q-factor is determined by

$Q_{S} = \frac{{wL}_{S}}{R_{S}}$

said w is the angular frequency of said power supply coil current, saidL_(S) is the inductance of said power supply coil, and said R_(S) is theresistance of said power supply coil.

Said pickup core may be of a plate form or lattice form.

Said pickup device may have an additional loop-type magnetic shieldmember installed around a pickup core.

Effect of the Invention

According to the present invention, it has an effect of providing apower supply and pickup system capable of maintaining stability ofefficiency of transmitting power to a pickup device from a power supplydevice even when a voltage or current changes due to the variation in aresonant frequency by setting Q-factor of a power supply and pickupsystem to a low value.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Drawing 1 shows a configuration of wireless power transmission systemfor electric vehicle.

Drawing 2 shows a mimetic diagram of a power supply device and a pickupdevice.

Drawing 3 shows a cross-sectional view at the front of a power supplydevice and a pickup device.

Drawing 4 shows a cross-sectional structure of a pickup device appliedto an electric vehicle.

Drawing 5 shows a magnetic field distribution when a technology ofshaped magnetic field in resonance is not applied.

Drawing 6 shows a magnetic field distribution when a technology ofshaped magnetic field in resonance is applied.

Drawing 7 shows a magnetic field distribution with magnetic flux densityvectors after a technology of shaped magnetic field in resonance isapplied.

Drawing 8 shows an equivalent circuit of wireless power transmissionsystem with a current source as a power source of a power supply device.

Drawing 9 shows an equivalent circuit of wireless power transmissionsystem with a voltage source as a power source of a power supply device.

Drawing 10 shows a structure of an I-shaped power supply device.

Drawing 11 shows an embodiment in which pickup cores in a pickup deviceare configured in a lattice-type.

Drawing 12 shows a power supply device modularized into the size of amagnetic pole interval to be easily installed in a curved road.

Drawing 13 shows an embodiment of a structure which copes with theproblem of expansion and contraction of a power supply device accordingto temperature change of a power supply device.

Drawing 14 shows a structure of a W-shaped power supply device.

Drawing 15 shows a magnetic shield method of an I-shaped power supplyand pickup device.

Drawing 16 shows transmission efficiency for the Q-factor (Q) of a powersupply device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 20 kHz.

Drawing 17 shows transmission efficiency for the Q-factor (Q) of a powersupply device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 18 kHz.

Drawing 18 shows transmission efficiency of the Q-factor (QL) of apickup device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 20 kHz.

Drawing 19 shows transmission efficiency of the Q-factor (QL) of apickup device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 18 kHz.

THE BEST FORM FOR EMBODIMENT OF THE INVENTION

From now on, desirable embodiments of the present invention will bedescribed in detail on reference to the attached drawings. Note that theterms or words used in the present specifications and the claims shouldnot be limited to common or lexical meanings but interpreted in suchmeanings and concepts corresponding to the technical idea of the presentinvention based on the principle that the inventor is able to properlydefine the concepts of terms to explain his or her invention using thebest method. Therefore, since the embodiments stated in the presentspecifications and the configurations indicated in the drawings aremerely the most desirable embodiments of the present invention but donot represent all the technical ideas of the present invention, itshould be understood that there might be various equivalences andvariations which can substitute for them.

Drawing 1 shows a configuration of wireless power transmission systemfor electric vehicle.

The power (60 Hz in the drawing) generated by an electric power companyis applied to the inverter which generates an electrical current ofwireless power transmission frequency (20 kHz in the drawing). Thegenerated current flows through a power supply coil (120) of the powersupply device. This results in magnetic field generated, and part of thegenerated magnetic field generates electric power due to a pickup coilin the pickup device (131). The generated power goes through a regulator(132) and is used to charge a battery (133) and drive a motor (134).

More specifically, an inverter (110), the source of power supply,functions to generate signals of wireless power transmission frequencyband. In the power supply device which transmits power wirelessly, thepower supply coil (120) acts as a kind of a transmission antenna; also,the power supply device must come with the SMFIR (shaped magnetic fieldin resonance) technology which decides the shape of magnetic fieldthrough metallic magnetic material or nonmetallic magnetic material suchas ferrite. The core element of the pickup device (131) is the pickupcoil and since a pure pickup coil alone is hard to make the path ofmagnetic field as it desires in the pickup device, the SMFIR technologywould be applied by the pickup core using metallic or nonmetallicmagnetic material, likewise the power supply device. For electricvehicles, load consists of a motor (134) or a battery (133) and consumesthe generated power.

Drawing 2 is a mimetic diagram of a power supply device and a pickupdevice.

When the electric current flows in a power supply coil (212) on a powersupply core (211) buried underground, magnetic field is generated. Whenthe generated magnetic field passes through a pickup coil (222) coiledaround a pickup core (221) of the pickup device, voltage is induced atboth ends of the pickup coil (induced electromotive force). Therefore,when resistive loads such as batteries or motors are connected to bothends of the pickup device, power is consumed at the loads.

Drawing 3 shows a cross-sectional view in front of a power supply deviceand a pickup device.

If a power supply core (311) of the power supply device is flat as shownin the drawing and hard to concentrate the paths of magnetic field intoa particular direction, the magnetic field generated from a power supplycoil (312) buried underground passes through a pickup coil (322) andforms a large loop on the whole as indicated by arrow 10. In this case,the capability of transferring power concentrated in the pickup devicedeclines. The power supply core (311) and the power pickup core (321)which controls the transfer direction of magnetic field may use ferrite.Like this, magnetic field shape control using magnetic ferrite is anessential element for the SMFIR technology.

Drawing 4 shows a cross-sectional structure of a pickup core (421) and apickup coil (422) applied to an electric vehicle (20).

Under the road, a flat power supply core (411) and a flat power supplycoil (412).

Drawing 5 shows a magnetic field distribution when the SMFIR technologyis not applied.

When the SMFIR technology is not applied, magnetic field is shaped in360 degrees around a power supply coil (510) where the electric currentflows and the whole magnetic field is equal to the sum of the magneticfield generated by each of the electric wires. The power supply device(transmission coil) and the pickup device (receiving coil) have roundedmagnetic fields, resulting in the distribution of magnetic field withtwo circles adjoining each other.

Drawing 6 shows a magnetic field distribution when the SMFIR technologyis applied.

When the SMFIR technology using magnetic material is applied, magneticfield is not radiated in 360 degrees; if there is magnetic material,magnetic field is well formed; otherwise, magnetic field is not wellformed. As shown in the drawing below, the reason why magnetic field isformed flatways at some position (610) is because there is magneticmaterial. This technology fundamentally functions to enhance thecapacity and efficiency of transmitting power by creating the path totransfer power through shaping magnetic field. In addition, like such acase that a pickup device is installed in the lower part of a vehicle,when a pickup device is installed in a limited space (height), it can beprevented that magnetic field spreads in all directions and affectsother devices or materials. Therefore, eddy current caused by magneticleakage field and the subsequent heat generation can be avoided andeffects of magnetic field on human body can be minimized.

Drawing 7 shows a magnetic field distribution with magnetic flux densityvectors after the SMFIR technology is applied

After the SMFIR technology is applied, magnetic field does not spread inall directions but follow the shaped path. The drawing below shows amagnetic field distribution with vectors after the SMFIR technology isapplied to a power supply device and a pickup device. An upward U-shapedstructure (710) is a metal plate of car body. When a pickup device isinstalled in the lower part of the car, the SMFIR technology must beapplied to prevent magnetic field from directly entering the car. Whenmagnetic field enters a metal plate perpendicularly, heat is generatedby eddy current, which is a big limitation for such a system that useshigh electric power such as a car. When the SMFIR technology is applied,there is a great advantage that magnetic field can be shaped not toenter a metal plate.

A thick arrow (720) on the left among the arrows arranged in the shapeof loop indicates the path of magnetic field transferred to a pickupdevice from a power supply device. Like this, the SMFIR technology canbe used to make the path of magnetic field in such a shape that isdesired by the designer, so that capacity and efficiency of pickupdevice may increase and magnetic leakage field indicated in high levelat a thin arrow (730) on the right decrease, resulting in the reducedeffect of magnetic field on human body.

Drawing 8 shows an equivalent circuit of wireless power transmissionsystem with a current source as a power source of a power supply deviceand Drawing 9 shows an equivalent circuit of wireless power transmissionsystem with a voltage source as a power source of a power supply device

From now on, an equation to calculate a power transfer function isdeduced based on Drawing 9.

The circuit on the left (910) shows an equivalent circuit of a powersupply device and the circuit on the right (920) shows an equivalentcircuit of a pickup device. We assume that the Q-factor of an equivalentcircuit of a power supply device is Q_(S) and the Q-factor of anequivalent circuit of a pickup device is Q_(L).

In the equivalent circuit of a power supply device (910),

$\begin{matrix}{{{\left( {R_{S} + \frac{1}{{jwC}_{S}} + {jwL}_{S}} \right)I_{1}} - {jwMI}_{2} - V_{S}} = 0} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In the equivalent circuit of a pickup device (920),

$\begin{matrix}{{{\left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right)I_{2}} - {jwMI}_{1}} = 0} & {{Equation}\mspace{14mu} 2}\end{matrix}$

From Equation 2

$\begin{matrix}{I_{1} = {\frac{R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}}{jwM}I_{2}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

By substituting Equation 3 into Equation 1,

$\begin{matrix}{I_{2} = {\frac{jwM}{\begin{matrix}{\left( {R_{S} + \frac{1}{{jwC}_{S}} + {jwL}_{S}} \right) \times} \\{\left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right) + {w^{2}M^{2}}}\end{matrix}}V_{S}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

can be obtained.

Meanwhile, the electric power of the equivalent circuit of a pickupdevice (920) can be obtained from the following equation

P _(L) =I ₂ ² ×R _(L)

and by substituting Equation 4 into this equation, we can obtain

$\begin{matrix}{P_{L} = {{\frac{{- w^{2}}M^{2}}{\begin{matrix}\left\lbrack {\left( {R_{S} + \frac{1}{{jwC}_{S}} + {jwL}_{S}} \right) \times} \right. \\\left. {\left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right) + {w^{2}M^{2}}} \right\rbrack^{2}\end{matrix}}}V_{S}^{2}R_{L}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Meanwhile, the electric power of the equivalent circuit of a powersupply device (910) can be obtained from the following equation

P _(S) =I ₁ ×V _(S)

and by substituting Equations 3 and 4 into this equation, we can obtain

$\begin{matrix}{P_{S} = {\frac{R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}}{\begin{matrix}{\left( {R_{S} + \frac{1}{{jwC}_{S}} + {jwL}_{S}} \right) \times} \\{\left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right) + {w^{2}M^{2}}}\end{matrix}}V_{S}^{2}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

From this, K, wireless power transfer function from a power supplydevice to a pickup device, is deduced from

$\begin{matrix}{K = {\frac{P_{L}}{P_{S}} = {\frac{w^{2}M^{2}R_{L}}{\begin{matrix}\left\lbrack {\left( {R_{S} + \frac{1}{{jwC}_{S}} + {jwL}_{S}} \right) \times} \right. \\{\left. {\left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right) + {w^{2}M^{2}}} \right\rbrack \left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right)}\end{matrix}}.}}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

From this equation

$K = {\frac{w^{2}M^{2}R_{L}}{\begin{matrix}\left\lbrack {\left( {R_{S} + \frac{1}{{jwC}_{S}} + {jwL}_{S}} \right) \times} \right. \\{\left. {\left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right) + {w^{2}M^{2}}} \right\rbrack \left( {R_{L} + \frac{1}{{jwC}_{L}} + {jwL}_{L}} \right)}\end{matrix}} - \frac{1}{\begin{matrix}\left\lbrack {{\left( {\frac{R_{S}}{wM} + {\frac{{jwL}_{S}}{wM}\left( {1 - \frac{1}{w^{2}L_{S}C_{S}}} \right)}} \right) \times \left( {\frac{R_{L}}{wM} + {\frac{{jwL}_{L}}{wM}\left( {1 - \frac{1}{w^{2}L_{L}C_{L}}} \right)}} \right)} + 1} \right\rbrack \\\left( {1 + \frac{1}{{jwR}_{L}C_{L}} + {{jw}\; \frac{L_{L}}{R_{L}}}} \right)\end{matrix}}}$

To this equation,

apply Q-factor

${Q_{MS} = \frac{wM}{R_{S}}},{Q_{ML} = \frac{wM}{R_{L}}},{Q_{S} = \frac{{wL}_{S}}{R_{S}}},{Q_{L} = \frac{{wL}_{L}}{R_{L}}}$

and apply a resonance frequency of the equivalent circuit of a powersupply device (910) and that of a pickup device (920)

${w_{OS} = \frac{1}{\sqrt{L_{S}C_{S}}}},{w_{OL} = \frac{1}{\sqrt{L_{L}C_{L}}}},$

then we can obtain

$\begin{matrix}{K = \frac{1}{\begin{matrix}\left\lbrack {\frac{1}{Q_{MS}Q_{ML}} \times \left( {1 + {{jQ}_{S} \times \left( {1 - \frac{w_{OS}^{2}}{w^{2}}} \right)}} \right) \times} \right. \\{\left. {\left( {1 + {{jQ}_{L} \times \left( {1 - \frac{w_{OL}^{2}}{w^{2}}} \right)}} \right) + 1} \right\rbrack \left( {1 + {{jQ}_{L} \times \left( {1 - \frac{w_{OL}^{2}}{w^{2}}} \right)}} \right)}\end{matrix}}} & {{Equation}\mspace{14mu} 8}\end{matrix}$

Meanwhile,

M=k√{square root over (L _(S) L _(L))}

is established, where k is coupling coefficient indicating how muchL_(S) and L_(L) are connected. From this,

${Q_{MS} \cdot Q_{ML}} = {{\frac{wM}{R_{S}} \cdot \frac{wM}{R_{L}}} = {\frac{w^{2}M^{2}}{R_{S}R_{L}} = {\frac{w^{2}k^{2}L_{S}L_{L}}{R_{S}R_{L}} = {{k^{2}\frac{{wL}_{S}}{R_{S}}\frac{{wL}_{L}}{R_{L}}} = {k^{2} \cdot Q_{S} \cdot Q_{L}}}}}}$

is established. When it is substituted into Equation 8,

$\begin{matrix}{K = \frac{1}{\begin{matrix}\left\lbrack {\frac{1}{k^{2}Q_{S}Q_{L}} \times \left( {1 + {{jQ}_{S} \times \left( {1 - \frac{w_{OS}^{2}}{w^{2}}} \right)}} \right) \times} \right. \\{\left. {\left( {1 + {{jQ}_{L} \times \left( {1 - \frac{w_{OL}^{2}}{w^{2}}} \right)}} \right) + 1} \right\rbrack \left( {1 + {{jQ}_{L} \times \left( {1 - \frac{w_{OL}^{2}}{w^{2}}} \right)}} \right)}\end{matrix}}} & {{Equation}\mspace{14mu} 9}\end{matrix}$

is established.

Drawing 10 shows a structure of an I-shaped power supply device.

A power supply device supplies the electric power to a moving object bymagnetic induction and a pickup device is attached to a moving object topick up the electric power from the power supply device by magneticinduction and charge batteries, etc. In this drawing, a top view (31), aside view (32) and a front view (33) of an I-shaped power supply deviceand a pickup device which picks up the electric power from the powersupply device are illustrated in the form of cross-sectional diagram.

This drawing shows an embodiment of an I-shaped power supply devicewhere the power supply device is buried under the road (1).

The I-shaped power supply device consists of a power supply core (1011)which has multiple magnetic poles (1012) arranged in series in thetraveling direction of a moving object and a feeder cable (1020) whichis placed so that each of the neighboring magnetic poles (1012) of saidpower supply core have different polarity from each other in thetraveling direction of a moving object, that is, the N pole and the Spole are generated in turn. In the embodiment of this drawing, theelectric current of opposing directions flow on two feeder cables (1020)and accordingly as shown in a side view (32), magnetic field (50) ofopposing directions is generated upwards from the consecutive magneticpoles (1012) and the N pole and the S pole are generated in turn. Inthis way, the electric power is supplied to the moving object travelingon the road via magnetic induction, and a pickup device (1040) picks upthe electric power from it. ‘I-shaped’ means that the cross section ofthe magnetic pole (1012) as shown in the front view (33) looks I-shaped.Of course, other shapes with slight changes or improvements are alsoavailable and collectively referred to as an ‘I-shaped’.

It is desirable that for said power supply core, as shown in thedrawing, the width perpendicular to the traveling direction of a movingobject is less than one half of the intervals between the centers ofsaid magnetic poles. As abovementioned, when an I-shaped magnetic poleis applied as shown in the drawing, the width of magnetic pole cansignificantly decrease and the N and S pole is generated in turn in thetraveling direction of the road, so that EMF at both ends of feedercable can significantly decrease and feeder cable installation cost candecrease. Besides, the distance between the buried power supply deviceand the pickup device installed in the lower part of a car, that is agap interval (1031, see Drawing 11), can be maintained to be more than acertain interval and the transferred electric power can be suppliedproperly. In addition, with a narrow width of feeder cable using anarrow I-shaped magnetic pole, the width of the pickup device installedin a car can decrease. In such a range, if the width of the pickupdevice exceeds a certain value, allowable deviation to the left andright may increase comparable with the feeder cable of other structure;this allows an additional benefit of having a larger allowable deviationrange in comparison with other structures.

As shown in the drawing, it is desirable that the length of saidmagnetic pole in the traveling direction of a moving object is more thantwo times of the distance between the neighboring ends of saidneighboring magnetic poles.

Meanwhile, said power supply core may be configured so that power supplymodules which have one or more magnetic poles arranged in series in thetraveling direction of a moving object are arranged in series in thetraveling direction of a moving object. That is, it may be of such ashape that power supply cores with magnetic poles are modularized andeach of the modules is connected in series.

Drawing 11 shows an embodiment in which a pickup core (1051) in a pickupdevice (1050) is configured in a lattice-type.

This may reduce the weight of the pickup core (1051) and have anadvantage in cooling and manufacturing in a mechanically soundstructure. In this case, there would be no significant effect onelectrical performance if the gap between the bars is as small as lessthan one half of the gap interval (1031).

Drawing 12 shows a power supply device modularized into the size of amagnetic pole interval to be easily installed in a curved road.

A top view (1210) and a side view (1220) of each of the power supplycore modules are presented here. At both ends of the power supply coremodule, there are connection members of male-female structure (1211,1212) which have large contact area in electromagnetic circuit and canbe easily connected. With this configuration, the power supply modulecan be combined onsite and slightly turned to the left or right incertain degrees along the bent road. A top view (1230) and a side view(1240) of the combination of the power supply core module with theconnection members (1211, 1212) are illustrated. Although not beingillustrated in this drawing, a core module which can be installed even abent road upwards or downwards such as a slope may be configured.

Drawing 13 shows an embodiment of a structure which is designed to solvethe problem of expansion and contraction of a power supply deviceaccording to temperature change of a power supply device.

The following are presented here: a top view (1310), a side view (1330),and the length of a power supply core (1311) of such a case that a powersupply device is subject to thermal contraction; and a top view (1320),a side view (1340), the length of a power supply core (1321), and afront view (1350) of such a case that a power supply device is subjectto thermal expansion.

A road should bear temperature changes ranging from −20° C. to +80° C.It should be considered that magnetic materials, cables, cableprotecting devices such as FRP or PVC pipe, asphalt or cement aresubject to thermal expansion and have different thermal expansioncoefficients. Also in this process, waterproof characteristics should bemaintained to be good.

Therefore, it is important that each of the structures should bediscontinued regularly in the traveling direction of the road and theaccess side should have waterproofing. Drawing 13 shows an example ofsuch a case that a connection member (1332) of magnetic material same asthe power supply core (1331) is installed in between the power supplycores (1331) in the traveling direction of the road. Also, FRP (fiberreinforced plastic) (1233) is cut and connected and the connecting areais treated with an O-ring (1334). The connection of FRP or PVC pipe mayuse such a method as contraction tube or bond connection. It is notnecessary to use flexible connection members all the time and flexibleconnection members may be used once every several meters or hundreds ofthousands of meters. Since cables are flexible in general, however, theabovementioned measures are usually unnecessary.

Drawing 14 shows a structure of a W-shaped power supply device.

In this drawing, a top view (41), a side view (42), and a front view(43) of a W-shaped power supply device and a pickup device which picksup the electric power from the W-shaped power supply device areillustrated in the form of cross-sectional view.

This drawing represents an embodiment of a W-shaped power supply devicewhich is buried under the road (1).

A W-shaped power supply device consists of a power supply core (1111)which is arranged in parallel to the traveling direction of a movingobject and has multiple magnetic poles (1112) arranged side by side, anda feeder cable (1120) which run in the traveling direction of a movingobject so that the neighboring magnetic poles of said power supply corein the side perpendicular to the traveling direction of a moving objecthave different polarity from each other, that is, the N pole and S poleare generated in turn. In an embodiment of this drawing, as shown in thefront view (43), the electric current of opposing directions flows ontwo feeder cables (1120) and as shown in the front view (43), themagnetic fields of opposing directions (60) are generated in themagnetic poles (1112) which are arranged in parallel to the travelingdirection of a moving object and run side by side, and the N pole and Spole are generated in turn. In this way, the electric power is suppliedto a moving object traveling on the road using magnetic induction and apickup device (1140) picks up the electric power from it. ‘W-shaped’means that the cross section of the power supply core (1111) includingthe magnetic poles (1112) as shown in a front view (43) looks W-shaped.Of course, other shapes with slight changes or improvements are alsoavailable. For example, there might be such a case where there is notmagnetic pole standing in the center of the front view (43) and only twoparallel magnetic poles, and accordingly, there is only a pair of N-Spoles. In this case, although a power supply device look U-shaped, it isreferred to as W-shaped. A W-shaped power supply device may beconfigured in such a shape that a power supply core of theabovementioned U-shaped power supply device is placed close to and inparallel with a moving body.

Meanwhile, said power supply core may be configured so that power supplymodules which have one or more magnetic poles arranged in series in thetraveling direction of a moving object are arranged in series in thetraveling direction of a moving object. That is, it may be of such ashape that power supply cores with magnetic poles are modularized andeach of the modules is connected in series.

Drawing 15 shows a magnetic shield method of an I-shaped power supplyand pickup device.

An I-shaped pickup device is characterized by that it can be reduced byhalf in size compared with the width of a car and bring about a spacefor magnetic shield. Therefore, as shown in Drawing 15, when a loop-typemagnetic shield material (1501) wraps around the device, magneticleakage flux is subject to magnetic ground along the magnetic shieldloop (1501), having an effect of magnetic shield. Magnetic shield can beperformed along the sides but it can also cover the top.

For an I-shaped power supply device, magnetic poles alternating atregular intervals generate EMF for the lateral direction. With anI-shaped magnetic shield line (1502) in the length direction as shown inDrawing 15, a magnetic shield effect is exercised by longitudinalmagnetic grounding.

Drawing 16 shows transmission efficiency for the Q-factor (Q_(S)) of apower supply device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 20 kHz.

A resonant frequency of a system may be changed depending uponmanufacturing process or errors of the component being used. Inparticular, when a pickup device moves but a power supply device isfixed as wireless charging electric car or additional pickup devicecollects power while there is a power supply device, a resonantfrequency of a system may be changed.

This drawing shows that a resonant frequency and an operating frequencyare matched (20 kHz). It is indicated that when Q_(S) is higher than 100(Q_(S)=115), the power transfer at operating frequency is slightlyimproved than when Q_(S) is smaller than 100 (Q_(S)=14.24)(0.872−>0.880; see the table below). However, when there is a differencebetween operating frequency and resonant frequency, the case where Q_(S)is smaller than 100 is far more advantageous than the case where Q_(S)is higher than 100, which is shown in Drawing 17 that will be explainedbelow.

Drawing 17 shows transmission efficiency for the Q-factor (Q_(S)) of apower supply device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 18 kHz.

As explained in reference to Drawing 16, when a resonant frequency of apower supply and pickup system and an operating frequency of the appliedsignal are matched, high power transfer function can be maintainedwithout being highly influenced by the Q-factor but if the Q-factor islarge, the frequency bandwidth becomes narrow and power transferfunction is greatly influenced by operating frequency.

When referring to Drawing 17, when resonant frequency is deviated fromoperating frequency like this, power transfer function is higher whenQ_(S) is smaller than 100 (Q_(S)=12.82) than when Q_(S) is higher than100 (Q_(S)=115) at the operating frequency (20 kHz) (0.055−>0.512; seethe table below). Like this, when resonant frequency (18 kHz) isdeviated from operating frequency (20 kHz) and fluctuates as shown inDrawing 17, power transfer function of wireless power transfer system isless sensitive when Q_(S) is smaller than 100 (Q_(S)=12.82) than whenQ_(S) is higher than 100 (Q_(S) =115) and more stable.

Therefore, it is desirable the Q-factor value of a power supply deviceis smaller than 100 for the stability of power transfer function when apower supply device is fixed but a power supply and pickup device isprone to be distorted due to the movement of a pickup device as theabovementioned wireless charging electric vehicle or additional pickupdevice collects more power while there is a power supply device. Inaddition, as internal pressure which the component of high power systemsuch as a power supply and pickup system for vehicle can bear is alsoimportant, it is desirable that the Q-factor of a power supply device issmaller than 100.

Drawing 18 shows transmission efficiency of the Q-factor (Q_(L)) of apickup device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 20 kHz. It shows that resonant frequency and operating frequency arematched (20 kHz). Power transfer function at operating frequency isbetter when Q_(L) is higher than 100 (Q_(L)=115) than when Q_(L) smallerthan 100 (Q_(L)=12.4) (0.873−>0.894, see the table below). However, whenthere is a difference between operating frequency and resonantfrequency, power transfer sensitivity is far more advantageous whenQ_(L) is smaller than 100 than when Q_(L) is higher than 100, which isshown in Drawing 19 that will be explained below.

Drawing 19 shows transmission efficiency of the Q-factor (Q_(L)) of apickup device with current signal of 20 kHz applied as operatingfrequency when a resonant frequency of a power supply and pickup systemis 18 kHz. Like this, when resonant frequency (18 kHz) is deviated fromoperating frequency (20 kHz), power transfer function is higher when isQ_(L) smaller than 100 (Q_(L)=11.2) than when Q_(L) is higher than 100(Q_(L)=115) at the operating frequency (20 kHz) (0.003−>0.094; see thetable below). Like this, when resonant frequency is deviated fromoperating frequency (20 kHz) and fluctuates as shown in Drawing 19,power transfer function of wireless power transfer system is lesssensitive when Q.sub.L is smaller than 100 (Q.sub.L=11.2) than Q.sub.Lis higher than 100 (Q.sub.L=115) and more stable.

What is claimed is:
 1. A power supply device supplying power to a movingobject using magnetic induction, the power supply device comprising: apower supply coil which is arranged to extend in a traveling directionof the moving object and through which a current flows to form amagnetic field; and a power supply core adjusting a direction of themagnetic field and having a plurality of magnetic poles extended to beparallel to the traveling direction of the moving object, wherein thepower supply core is arranged with respect to the power supply coil sothat two neighboring magnetic poles of the power supply core havedifferent magnetic polarities and a direction of the magnetic field atthe magnetic poles of the power supply core is perpendicular to thetraveling direction of the moving object, and wherein Q-factor of thepower supply device is less than 100, said Q-factor is determined by${{Qs} = \frac{wLs}{Rs}},$ wherein said w is an angular frequency of thecurrent, said L_(S) is an inductance of said power supply device, andsaid R_(S) is a resistance of said power supply device, wherein a crosssection of the power supply core perpendicular to the travelingdirection of the moving object has a I-shape and said power supply coilis arranged in parallel to the traveling direction of the moving objectin the power supply core.
 2. The power supply device of claim 1, whereinthe magnetic poles of the power supply core are arranged in series inthe traveling direction of the moving body, and the power supply coil isarranged in parallel to the traveling direction of the moving body onboth sides of said magnetic poles and intersect each other between saidmagnetic poles.
 3. The power supply device of claim 1, furthercomprising a linear magnetic shield member installed in the travelingdirection.
 4. The power supply device of claim 1, wherein said powersupply core is formed of a plurality of power supply modules which haveone or more magnetic poles arranged in series in the traveling directionof the moving object arranged on lines in series in the travelingdirection.
 5. The power supply device of claim 4, wherein each of saidpower supply modules has core connection parts at front and rear endsand the power supply modules are connected to each other by said coreconnection parts and arranged on lines in series in the travelingdirection.
 6. The power supply device of claim 4, wherein said powersupply modules are arranged to be spaced apart from each other to acceptthermal expansion and thermal contraction.
 7. The power supply device ofclaim 4, wherein said power supply core has a glass fiber reinforcedplastic which is installed at an upper part or a lower part.
 8. A powersupply device supplying power to a moving object using magneticinduction, the power supply device comprising: a power supply coil whichis arranged to extend in a traveling direction of the moving object andthrough which a current flows to form a magnetic field; and a powersupply core adjusting a direction of the magnetic field and having aplurality of magnetic poles extended to be parallel to the travelingdirection of the moving object, wherein the power supply core isarranged with respect to the power supply coil so that two neighboringmagnetic poles of the power supply core have different magneticpolarities and a direction of the magnetic field at the magnetic polesof the power supply core is perpendicular to the traveling direction ofthe moving object, and wherein Q-factor of the power supply device isless than 100, said Q-factor is determined by ${{Qs} = \frac{wLs}{Rs}},$wherein said w is an angular frequency of the current, said L_(S) is aninductance of said power supply device, and said R_(S) is a resistanceof said power supply device, wherein a cross section of the power supplycore perpendicular to the traveling direction of the moving object has apair of I-shapes adjoining each other and said power supply coil isarranged in parallel to the traveling direction of the moving object inthe power supply core, wherein said power supply coil is disposed ineach of said I-shapes.